1. Technical Field
This disclosure relates to a method of fabricating a semiconductor device and, more particularly, to a method of fabricating a cylinder-type capacitor.
2. Description of the Related Art
Recently, as semiconductor devices have become more highly integrated, design rules for fabricating the semiconductor devices have decreased. As a result, the regions available for forming capacitors are also being decreased. Generally, the capacitance of a capacitor is proportional to the dielectric constant of the dielectric film and the surface area of the electrodes. It is desirable to fabricate a capacitor with high capacitance in order to provide reliable data storage between refresh cycles in the semiconductor device. Thus, in order to form a capacitor having high capacitance in a narrow area, the dielectric film should be formed of a material having high dielectric constant (i.e. a high-k material), or the surface area of the electrodes should be increased. However, introducing high-K materials into existing manufacturing processes presents problems like requiring new manufacturing equipment, presenting reliability concerns of the dielectric films, and the feasibility of mass-production. Therefore, in order to ensure adequate capacitance required for highly integrated semiconductor devices with conventional dielectric films, it is necessary to increase the surface area of the electrodes.
Therefore, recently, the demand for capacitors having a cylinder-type storage electrode which has increased height and small intervals between nodes, that is, a cylinder-type storage electrode with a large aspect ratio, is increasing.
A method of forming a conventional cylinder-type capacitor is described below.
The method comprises forming an etch stop film on an interlayer insulating film including contact plugs and then forming an insulating film for a mold with a height in accordance with the desired height of the storage electrode for the cylinder-type capacitor. Next, the insulating film and the etch stop film are sequentially etched to complete a mold defining an opening which exposes the contact plugs. Finally, conductive polysilicon is deposited in the opening, the electrodes are separated by cells to form the cylinder-type storage electrode, and then the mold is removed by a wet etching process.
In the meantime, water may remain between the storage electrodes when the mold is removed by wet etching. Since water has high surface tension, leaning may occur between storage electrodes, forming a bridge therebetween during the subsequent wet and dry etching processes. Due to this leaning phenomenon, which causes the storage electrodes to be bridged, the characteristics of semiconductor devices are often deteriorated. As the aspect ratio increases, the leaning occurs more frequently.
In addition, during the wet etching process for removing the mold, etchant may permeate into the interface between the storage electrode and the etch stop film. Thus, defects may occur in a lower membrane under the etch stop film.
Therefore, the demand for cylinder-type capacitors having a large aspect ratio, low occurrence of bridging between the electrodes, and low membrane defects, is increasing.
The invention addresses these and other disadvantages of the conventional art.